"You have opted to censor the internet. This is why we, Anonymous, have decided that this censorship plan should be among our primary targets for elimination," the group wrote.

"Firstly: We demand the abolition of the censorship plan proposed by the current government. This includes the removal of all targets on the blacklist, and complete abandonment of any further plans and endeavors by the Australian Government to censor the internet

"Secondly: We demand the resignation of the Australian Minister for Broadband, Communications and the Digital Economy, Stephen Conroy.

"This is a man who has no level of understanding of the topic he is dealing with. This is a man who readily supports the abolition of free speech in exchange for social security. This man and his policies go against everything Australia and the western world stand for.

"As we see it, Stephen Conroy is completely unsuitable of being a minister of Australia, and as such, we demand his dismissal.

"Failure to meet these demands will result in our full-fledged wrath. This is not something you want to happen."

"In two minutes from when I type this, Anonymous is declaring war on the Australian Government over its decision to implement Draconian internet censorship," the posting said.

"Tick tick tick.

"Update: 7pm: and so it begins.

"7:05pm (AEST), Ministers page is slow to load, but still up."

"7:11pm we've confirmed on site (via a source) that the sites due to be attacked have been taken down from the coordination page, possibly before the raid."

"7:18pm pm.gov.au DOWN!

"7:21pm Kevin Rudd's page is down completely. Strike one to Anonymous."

The hacker then suggests in a subsequent message posting that the attack may have failed.

However, a check of the prime minister's website more than an hour after the attack began confirmed it was down.

A spokesman for Senator Conroy said he had received reports of the hack but could not confirm whether the attack had been successful.

However, he said the people responsible were misguided, adding that the proposed filter would only be used to block illegal content.

"The campaign that they're mounting is erroneous and misinformed," he said.

"What the government is proposing is to filter refused classification content which includes imagery of child sexual abuse, rape and bestiality."

The government has been conducting an internet filter trial which is expected to be completed soon.

A report will then be presented to Senator Conroy from which an internet filter policy will be developed.